Medical or dental handpiece

ABSTRACT

Embodiments of a medical or dental handpiece are disclosed. A medical or dental handpiece may include a rotatable drive element to drive a tool that can be connected to the handpiece, a rotational speed measuring device which is designed to generate a variable electric rotational speed measurement signal assigned to the rotational speed of the drive element, a lighting device that can be supplied with electric power for emitting radiation, in particular visible light, onto a treatment site, and at least one shared electric line, which is provided for transmitting electric power to the illumination device and the rotational speed measurement signal of the rotational speed measurement device. Further a corresponding method for the operation of a medical or dental handpiece is disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This is a continaution of U.S. patent application Ser. No. 14/693,201,filed Apr. 22, 2015, which is a continuation of InternationalApplication No. PCT/EP2013/072970, filed Nov. 5, 2013, which waspublished in German under PCT Article 21(2), which in turn claims thebenefit of abandoned European Patent Application No. EP 12191193.7,filed Nov. 5, 2012, and from pending European Patent Application No. EP12195365.7, filed Dec. 4, 2012, which are incorporated herein byreference.

BACKGROUND

Field

The present invention relates to a medical or dental handpiece having arotational speed measuring device ⁻for measuring the rotational speed ofa drive element of the handpiece that can he connected to a tool.

Description of Prior Art

U.S. Pat. No. 4,493,643 discloses such a medical or dental handpiecehaving a rotational speed measuring device arranged in a head section ofthe handpiece.

SUMMARY

It is an object to optimize the implementation or the installationsituation of the rotational speed measuring device, in particular of arotational speed sensor on the handpiece, preferably in the head sectionof the handpiece, so that the rotational speed measuring device, inparticular the rotational speed sensor, can be arranged and operated inthe handpiece, in particular in or adjacent the head section of thehandpiece, despite the large number components and the very limitedavailable space.

This object is achieved by a medical or dental handpiece comprising: adrive element that can he induced to rotate for driving a tool that canbe connected to the handpiece, a rotational speed measuring device thatis designed to generate a variable electric rotational speed measurementsignal assigned to the rotational speed of the drive element, a lightingdevice that can be supplied with electric power for emitting radiation,in particular visible light, onto a treatment site and at least oneshared electric line, which is provided for transmitting the electricpower (the electric power supply signal) to the lighting device and therotational speed measurement signal of the rotational speed measuringdevice.

Thus, advantageously a shared electric signal line or electric powersupply fine is created for the rotational speed measuring device, inparticular for the rotational speed sensor, and for the lighting deviceso that the electric measurement signals of the rotational speedmeasuring device and the electric (power supply) signals of the lightingdevice can be conducted over said line. This eliminates the need toprovide a separate electric line and separate electric connections forthe rotational speed measuring device and the lighting device, so thatthe space available in the interior of the handpiece is utilized moreeffectively, and furthermore, the design of the handpiece, in particularin the coupling region, is simplified.

The rotational speed measuring device is preferably designed as aninductive rotational speed measuring device or comprises an inductiverotational speed sensor. The inductive rotational speed sensor or theinductive rotational speed measuring device preferably comprises amagnetic element and at least one measuring coil, which can be movedrelative to one another. In particular the magnetic element is arrangedon or attached to the drive element for driving a tool that can beconnected to the handpiece, for example, an impeller. The measuring coilis preferably connected to or attached to a component of the handpiecewhich is rotationally fixed with respect to the drive element, forexample, the outer sleeve. Preferably the inductive rotational speedmeasuring device additionally comprises at least one soft magneticelement to concentrate the magnetic field of the magnetic element. Thesoft magnetic element is provided in or on the measuring coil inparticular. The inductive rotational speed measuring device is designedin particular to generate an electric rotational speed measurementsignal, which is designed as an alternating signal, for example, as asinusoidal or pulse-shaped electric alternating signal or alternatingcurrent signal.

The handpiece may clearly also have an alternative rotational speedmeasuring device or an alternative rotational speed sensor, which aredesigned, for example, as a capacitive or optical rotational speedmeasuring device or rotational speed sensor or as a rotational speedmeasuring device by means of eddy currents and which generate inparticular an electric rotational speed measurement signal. The opticalrotational speed measuring device comprises, for example, a radiationsource, at least one reflector that is provided on the drive element forthe light that can be emitted by the radiation source and a receivingdevice for the radiation reflected by the reflector. A capacitiverotational speed measuring device comprises, for example, a capacitorand an element provided on the drive element for changing thecapacitance of the capacitor. A rotational speed measuring device or arotational speed sensor, which does not directly generate an electricrotational speed measurement signal, for example, an optical rotationalspeed sensor, is preferably connected to a converter device, forexample, an electronic converter, which converts the rotational speedmeasurement signal, for example, an optical signal, into an electricrotational speed measurement signal.

The lighting device and at least a part of the rotational speedmeasuring device, in particular the at least one measuring coil of theinductive rotational speed measuring device, are preferably arrangedelectrically in series. The electric power (the electric power supplysignal) is or will thus be supplied to the lighting device over at leasta portion of the rotational speed measuring device, in particular overthe at least one measuring coil of the inductive rotational speedmeasuring device. The measuring coil is preferably designed as alow-resistance measuring coil.

The drive element is preferably mounted rotatably in the handpiece bymeans of at least one hearing, in particular a roller bearing. The driveelement is in particular preferably designed as an impeller, which canbe driven or induced to rotate by a compressed gas. Alternatively, thedrive element is designed as a shaft or a hollow shaft that can beinduced to rotate.

The lighting device for emitting radiation onto a treatment sitepreferably comprises one or more, for example, three, four or fiveoptical semiconductor elements, in particular light-emitting diodes(LEDs). However, the lighting device may clearly also have otherradiation sources, for example, at least one incandescent bulb or atleast one gas discharge lamp. The lighting device, in particular the atleast one optical semiconductor element, is preferably arranged eitheron the head section of the handpiece, in particular around a toolreceptacle opening on the headpiece, or adjacent to the head section.The lighting device is provided in particular on the side of thehandpiece, on which a tool receptacle opening of the handpiece issituated. The lighting device is designed in a ring shape in particular,preferably surrounding the tool receptacle opening of the head section.The tool can be connected to the drive element in particular through aninternal bore of the ring-shaped lighting device, for example, beinginsertable into or removable from a tool mount on the handpiece. Atleast one opening and/or one channel through which a fluid, inparticular a cooling medium, for example, a water-air mixture can bedispensed in the direction of the treatment site is preferably providedin or on the body of the lighting device.

The shared electric line provided in the handpiece, comprising one ormore line wires, for example, connects the lighting device to anelectric power source, in particular to a constant current source and/ora constant voltage source. The shared electric line provided in thehandpiece also connects in particular at least a part of the rotationalspeed measuring device, for example, its measuring coil, to the electricpower source, in particular to the constant current source and/or to theconstant voltage source, or the lighting device via at least a part ofthe rotational speed measuring device, for example, its measuring coil,to the electric power source. The shared electric line provided in thehandpiece is provided for shared and preferably simultaneoustransmission of electric signals of two different electric powersources, in particular of the electric power source (constant currentsource and/or constant voltage source) for supplying power to thelighting device with a substantially constant electric signal and therotational speed measuring device. The two electric signals, forexample, the electric power supply signal for the lighting device andthe rotational speed measurement signal in particular form a mixedelectric signal.

The electric power source, for example, a constant current source and/ora constant voltage source, is designed to supply the lighting devicewith a substantially constant electric signal, in particular with aconstant current or a d.c. current or a d.c. voltage. If, according toone embodiment, exclusively a constant voltage source (and not aconstant current source) is provided as the electric power source, thenthe lighting device comprises, for example, an incandescent bulb or anoptical semiconductor element, for example, a light-emitting diodehaving a series resistor. The electric power source may be arranged inthe handpiece or may be provided outside of the handpiece, for example,in an adaptor or coupling part that can be connected to the handpiece orin a supply unit or in a control unit and/or regulating unit. Thus,according to one embodiment, a medical or dental treatment device iscreated having a handpiece with a shared electric line for transmissionof the electric power (the power supply signal) to the lighting deviceand for transmission of the electric rotational speed measurement signalof the rotational speed measuring device and an electric power sourcefor supplying power to the lighting device, wherein the handpiece andthe electric power source are preferably detachable from one another.The electric power source, which is provided in the handpiece inparticular, comprises a battery, an accumulator or a generator, forexample, which is preferably connected to an electric rectifier.

The electric power source preferably comprises a constant current sourceor a constant voltage source, which is designed to receive a mixedelectric signal which comprises the variable electric rotational speedmeasurement signal which is generated by the rotational speed measuringdevice and is assigned to the rotational speed of the drive element andto correct this variable electric rotational speed measurement signal bymeans of a first variable electric correction signal, such that thesubstantially constant electric signal is available for the power supplyto the lighting device. The variable electric rotational speedmeasurement signal comprises in particular a sinusoidal or pulse-shapedelectric signal generated by the rotational speed measuring device. Themixed electric signal additionally comprises in particular thesubstantially constant electric signal for the power supply to thelighting device, which is supplied by the constant current source or theconstant voltage source. In other words, two electric power sources (theconstant current source or the constant voltage source and therotational speed measuring device) are thus provided, their electricsignals (the constant electric signal and the variable electricrotational speed measurement signal) being superimposed and forming themixed electric signal, and their electric signals being transmitted ortransmissible, in particular simultaneously, over the shared electricline.

The constant current source or the constant voltage source is designedas an electric or electronic regulating device in particular. Theconstant current source or constant voltage source is preferablydesigned to generate a first variable electric correction signal to makeavailable the substantially constant electric signal to the lightingdevice. The constant current source or the constant voltage source isthus preferably designed to generate a first variable sinusoidal orpulse-shaped electric correction signal, which counteracts or equalizesthe variable electric rotational speed measurement signal of the mixedelectric signal or the variable component of the mixed electric signal.

According to one embodiment, the medical or dental treatment devicecomprises an evaluation unit, which is designed to determine therotational speed of the drive element on the basis of the variableelectric rotational speed measurement signal or the first variableelectric correction signal of the constant current source or theconstant voltage source. The evaluation unit is preferably connected(electrically) to the constant current source or the constant voltagesource and/or at least one part of the rotational speed measuringdevice, in particular the measuring coil of the inductive rotationalspeed measuring device. The evaluation unit is preferably designed todetect or receive the variable electric rotational speed measurementsignal or the first variable electric correction signal of the constantcurrent source or of the constant voltage source and in particular todetermine the rotational speed of the drive element on the basis of thefrequency of one of these two signals. The frequency of the correctionsignal corresponds to or represents the frequency of the rotationalspeed measurement signal of the rotational speed measuring device. Theevaluation unit comprises a microcontroller in particular. Theevaluation unit preferably comprises at least one device for processingthe variable electric rotational speed measurement signal or the firstcorrection signal, for example, an analog-digital converter or a signalfilter.

The medical or dental treatment device preferably comprises a controlunit and/or regulating unit, which is designed to control and/orregulate the rotational speed of the drive element on the basis of therotational speed determined by the evaluation unit, in particular suchthat the drive element can be operated at a constant rotational speed.The control unit and/or regulating unit preferably comprises and/orcontrols and/or regulates an adjusting element, for example, a valve, inparticular a solenoid valve, which is designed to act on the compressedgas driving the drive element, for example, the impeller. The adjustingelement adjusts the flow rate and/or the gas pressure of the compressedgas for driving the drive element in particular. The control unit and/orregulating unit comprise(s) a microcontroller in particular. A sharedmicrocontroller comprising the evaluation unit and the control unitand/or regulating unit is preferably provided.

According to one embodiment, a temperature sensor, which is designed togenerate a variable electric temperature measurement signal, is providedin the medical or dental handpiece, in particular in its head section,and is connected in parallel electrically to the lighting device,wherein the shared electric line is provided for transmission of thetemperature measurement signal. The temperature sensor is preferablyelectrically connected to the electric power source, for example, theconstant current source or the constant voltage source, and inparticular can he supplied with electric power by such a source.

The temperature sensor comprises, for example, a sensor having amaterial whose electric resistance is a function of temperature, inparticular an NTC resistor or a PTC resistor, an infrared sensor or athermocouple. The temperature sensor in particular is designed todetermine the temperature of the handpiece, in particular thetemperature in the interior of the handpiece and/or the temperature ofat least one component of the handpiece. The temperature sensor ispreferably arranged in or on or attached to a component of thehandpiece, for example, the outer sleeve, the lighting device or abearing. Alternatively, the temperature sensor is arranged freely in aninterior space of the handpiece and is mounted substantially only on anelectric signal line. The temperature sensor may have one or moresensors. The temperature sensor is designed to generate a temperaturemeasurement signal, for example, by a change in a parameter of anelectric power signal sent to the temperature sensor as a function ofthe temperature, for example, the amperage.

According to one embodiment, the constant current source or the constantvoltage source of the medical or dental treatment device is designed toreceive a mixed electric signal which comprises the variable electrictemperature measurement signal generated by the temperature sensor andto correct this variable electric temperature measurement signal bymeans of a second variable electric correction signal, such that asubstantially constant electric signal for the power supply to thelighting device is provided. Three electric power sources (the constantcurrent source or the constant voltage source, the rotational speedmeasuring device and the temperature sensor) are thus especiallypreferably provided and their electric signals (the constant electricpower supply signal, the variable electric rotational speed measurementsignal and the variable electric temperature measurement signal) aresuperimposed and form the mixed electric signal and their electricsignals are transmitted or are transmissible, in particularsimultaneously, over the shared electric line.

An evaluation unit connected to the temperature sensor or to theconstant current source or to the constant voltage source is preferablyprovided and is designed to determine the temperature measured by thetemperature sensor on the basis of the temperature measurement signal orthe second variable electric correction signal of the constant currentsource or the constant voltage source. A single evaluation unit (in theform of a microcontroller) is provided and is designed to determine therotational speed of the drive element in particular on the basis of thefirst variable electric correction signal of the constant current sourceor the constant voltage source and to determine the temperature measuredby the temperature sensor on the basis of the second variable electriccorrection signal of the constant current source or the constant voltagesource.

The control unit and/or regulating unit is/are preferably designed togenerate a warning signal on reaching or exceeding a temperature limitvalue and/or to interrupt the operation of the handpiece or of thetreatment device or of the drive element.

The medical or dental treatment device preferably comprises a warningdevice or a display device which is designed to display the rotationalspeed of the drive element determined by the rotational speed measuringdevice and/or the temperature value determined by the temperaturesensor. The display device is operatively connected to the control unitand/or the regulating unit in particular.

A method for operating a medical or dental handpiece is defined by thefact that the electric power (the electric power supply signal) for thelighting device and the rotational speed measurement signal of therotational speed measuring device are transmitted over the at least oneshared electric line.

A method for operating a medical or dental treatment device is definedby the method described above for operating a medical or dentalhandpiece, wherein the evaluation unit additionally determines therotational speed of the drive element on the basis of the variableelectric rotational speed measurement signal or the first variableelectric correction signal of the constant current source or theconstant voltage source. The constant current source or the constantvoltage source preferably receives a mixed electric signal, whichcomprises the variable electric rotational speed measurement signal thatis generated by the rotational speed measuring device and is assigned tothe rotational speed of the drive element and corrects this variableelectric rotational speed measurement signal by means of a firstvariable electric correction signal, such that the substantiallyconstant electric signal for the power supply to the lighting device isprovided. The control unit and/or regulating unit especially preferablycontrols and/or regulates the rotational speed of the drive element onthe basis of the rotational speed determined by the evaluation unit andin particular by comparison of the rotational speed determined by theevaluation unit with a predetermined setpoint rotational speed, inparticular such that the drive element is operated at a constantrotational speed. The evaluation unit preferably determines thetemperature measured by the temperature sensor on the basis of thetemperature measurement signal or of the second variable electriccorrection signal of the constant current source or the constant voltagesource.

These and other embodiments will be described below with reference tothe following drawings

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of a medical or dental handpiece having ashared electric line for the transmission of electric power to thelighting device and of a rotational speed measurement signal of arotational speed measuring device.

FIG. 2 shows an embodiment of a medical or dental treatment devicehaving a handpiece according to FIG. 1.

FIG. 3 shows a schematic diagram of an electric control or regulatingcircuit for controlling or regulating the rotational speed of a driveelement having a shared electric line for transmission of electric powerto the lighting device and of a rotational speed measurement signal of arotational speed measuring device.

FIG. 4 shows in a schematic diagram the composition and thecharacteristic of a mixed electric signal over time, comprising thevariable electric rotational speed measurement signal generated by therotational speed measuring device and assigned to the rotational speedof the drive element, and comprising the substantially constant electricsignal supplied by the electric power source to supply power to thelighting device.

FIG. 5 shows a schematic diagram of a detail of an electric control orregulating circuit to control or regulate the rotational speed of adrive element and to measure the temperature, wherein a shared electricline is provided for transmission of electric power to the lightingdevice, for transmission of a rotational speed measurement signal of arotational speed measuring device and for transmission of a temperaturemeasurement signal of a temperature sensor.

DETAILED DESCRIPTION

The medical or dental handpiece 1 of FIGS. 1 and 2 comprises a handlesection 1A and a head section 1B. An outer sleeve 15 surrounds thehandpiece. The handpiece 1 is designed as a handpiece operated withcompressed gas, in particular compressed air, and comprises in its headsection 1B a drive element 3, which can be set in rotation, inparticular in the form of an impeller 3′ that can be acted upon withcompressed gas. The compressed gas can be supplied to the drive element3 over a compressed gas line (not shown) extending through the handpiece1. A shaft or a hollow shaft 3″ is a part of or connected to the driveelement 3 and is designed to receive a tool that can be connected to thehandpiece 1. The hollow shaft 3″ is thus also a part of a tool holdingdevice 16 arranged in the head section 1B for releasable accommodationof a tool, in particular a drill that can be set in rotation. Two rollerbearings 19 are provided for rotational support of the drive element 3in the head section 1B. A tool receptacle opening 18 provided laterallyon the head section 1B is connected to the tool holding device 16. Atool release device 17 is designed to release the tool from the toolholding device 16, so that it can be removed by a user.

A lighting device 2 for emitting radiation onto a treatment site isprovided in an opening on the outer sleeve 15, preferably in the headsection 1B, or connected thereto. The lighting device 2 comprises atleast one light source to which electric power can be supplied,preferably at least one optical semiconductor element, for example, alight-emitting diode. Preferably a plurality of optical semiconductorelements can be arranged electrically in parallel or in series, inparticular being positioned around the tool receptacle opening 18. Anelectric power source 11 (see FIGS. 2 and 3), for example, a constantcurrent source and/or a constant voltage source is provided to supply asubstantially constant electric signal, in particular a constant voltageor constant current or direct current 5′, to the lighting device 2 (seeFIG. 4).

To measure the rotational speed of the drive element 3, in particular ofthe impeller 3′, a rotational speed measuring device 4 is provided inthe handpiece 1. At least a portion of the rotational speed measuringdevice 4 is arranged near or adjacent to the drive element 3, preferablyin the head section 1B of the handpiece 1. The rotational speedmeasuring device 4 of the handpiece 1 of FIG. 1 is designed as aninductive rotational speed measuring device having a magnetic element 7and a measuring coil 8. The magnetic element 7 is preferably connectedto the drive dement 3, in particular to the impeller 3′ or alternativelyto the shaft 3″, such that it can be set in rotation with the driveelement 3. The magnetic element 7 may have, for example, a ring-shapedor toroidal magnet or multiple individual magnetic elements. Themeasuring coil 8, which is preferably equipped with a soft magneticcore, is positioned close to the magnetic element 7 and in arotationally fixed position with respect to the drive element 3. Arelative movement between the magnetic element 7 and the measuring coil8 is induced by the rotation of the drive element 3, and a sinusoidal orpulse-shaped electric alternating signal is generated inductively. Therotational speed measuring device 4 thus forms an electric power source,which generates a variable electric rotational speed measurement signal5 assigned to the rotational speed of the drive element 3 (see FIG. 4).

Further, a shared electric line 6 is provided in the handpiece 1, whichis designed for transmission of electric power or an electric powersupply signal 5′ to the lighting device 2 and of the rotational speedmeasurement signal 5 of the rotational speed measuring device 4. Asshown in FIG. 1, the rotational speed measuring device 4 and thelighting device 2, in particular the measuring coil 8, are arranged inseries electrically. The lighting device 2 and the measuring coil 8 arepreferably attached directly to one another or to a shared carrier, forexample, a circuit board.

FIG. 2 shows the design of a medical or dental treatment device 10comprising the handpiece 1, an electric power source 11, for example, aconstant current source or constant voltage source, which is designed tosupply a substantially constant electric signal 5′ to the lightingdevice 2, an evaluation unit 12, which is designed to determine therotational speed of the drive element 3, and a control unit and/or aregulating unit 13, which is designed to control and/or regulate therotational speed of the drive element 3 on the basis of the rotationalspeed determined by the evaluation unit 12. A clamping block (not shown)is preferably provided, connecting at least the electric lines of thelighting device 2 and the rotational speed measuring device 4,optionally also connecting further components that can be operated withelectric power. A single microcontroller is preferably provided,comprising at least the evaluation unit 12 and the control unit and/orregulating unit 13. In particular the evaluation unit 12 and the controlunit and/or regulating unit 13, preferably also the electric powersource 11, may be arranged in a supply unit 20 that is preferablydetachable from the handpiece 1. The supply unit 20 preferably alsocomprises a connection to a compressed air source and optionally also toother media sources, for example, to a water supply. A supply hose 21and a coupling device 22, which is detachable in particular, connect thesupply unit 20 to the handpiece 1. In particular the shared electricline 6 and/or an electric line connected thereto extend(s) through thehandpiece 1, the coupling device 22 and the supply hose 21 up to theelectric power source 11, the evaluation unit 12 or the control unitand/or regulating unit 13.

FIG. 3 shows a schematic diagram of an electric control or regulatingcircuit for control or regulation of the rotational speed of the driveelement 3. The diagram shows the components already described inconjunction with the handpiece 1, i.e., the lighting device 2, the driveelement 3, the rotational speed measuring device 4 with the measuringcoil 8 and the magnetic element 7 as well as the shared electric line 6.An electric power source of the treatment device 10 comprises theconstant current source 11 and a constant voltage source 23, wherein thetwo electric sources 11, 23 are preferably connected to one anotherelectrically. The constant current source 11 and/or the constant voltagesource 23 is/are designed to supply electric power (the substantiallyconstant electric signal 5′) to the lighting device 2 via the measuringcoil 8 and the shared electric line 6. The constant voltage source orthe constant current source 11 is also designed as an electric orelectronic regulating device in particular, which regulates the electricpower supply to the lighting device 2 substantially at a predefinedlevel of the constant voltage or constant current 5′, preferablytogether with a shunt resistor 24.

If the drive element 3 and the magnetic element 7 connected to it areset in rotation, the rotational speed measuring device 4 generates, asdescribed above, a variable electric rotational speed measurement signal5, which is applied to the shared electric line 6. The shared electricline 6 thus conducts a mixed electric signal, comprising the variableelectric rotational speed measurement signal 5 which is generated by therotational speed measuring device 4 and is assigned to the rotationalspeed of the drive element 3 and the substantially constant electricsignal 5′ (see FIG. 4). In other words, the constant electric signal 5′and the variable electric rotational speed measurement signal 5 aresuperimposed and form the mixed electric signal.

The constant current source or the constant voltage source 11 isdesigned to receive the mixed electric signal and to correct itsvariable (sinusoidal or pulse-shaped) component, i.e., the variableelectric rotational speed measurement signal 5, by means of a firstvariable electric correction signal, such that the substantiallyconstant electric signal 5′ for the power supply to the lighting device2 is provided. The evaluation unit 12, which is electrically connectedto the constant current source or the constant voltage source 11, isdesigned to determine the rotational speed of the drive element 3 on thebasis of the first variable electric correction signal of the constantcurrent source or the constant voltage source 11 or to determine therotational speed of the drive element 3 directly on the basis of thevariable electric rotational speed measurement signal 5. The evaluationunit 12 is preferably designed to detect or pick up the first variableelectric correction signal of the constant current source or theconstant voltage source 11 or the variable electric rotational speedmeasurement signal 5 and in particular to determine the rotational speedof the drive element 3 on the basis of the frequency of the firstcorrection signal or of the rotational speed measurement signal 5. Thefrequency of the correction signal corresponds to the frequency of therotational speed measurement signal 5 of the rotational speed measuringdevice 4. Preferably at least one device 25 for processing the firstcorrection signal or the rotational speed measurement signal 5, forexample, an analog-digital converter or a signal filter is connectedupstream to the evaluation unit 12 or is designed as part of it.

The evaluation unit 12 is electrically connected to a control unitand/or regulating unit 13. The control unit and/or regulating unit 13 isdesigned to control and/or regulate the rotational speed of the driveelement 3 on the basis of the rotational speed determined by theevaluation unit 12, in particular such that the drive element 3 can beoperated at a constant rotational speed. The control or regulation ispreferably accomplished by comparing the rotational speed determined bythe evaluation unit 12 with a predefined setpoint rotational speed.Preferably, an adjusting element is provided which is connected to thecontrol unit and/or regulating unit 13 and is designed for specifying asetpoint rotational speed value. The control unit and/or regulating unit13 comprises an adjusting element 14 or is connected to an adjustingelement 14, which is designed to act on the compressed gas driving thedrive element 3. The adjusting element 14 is designed in particular as avalve, for example, as a proportional valve or a solenoid valve. Theadjusting element 14 is in particular designed to adjust the gaspressure and/or the volume flow of the compressed gas.

FIG. 5 shows a schematic diagram of a detail of an electric control orregulating circuit for control or regulation of the rotational speed ofa drive element 3 and for measuring the temperature, wherein a sharedelectric line 6 is provided for transmission of electric power to thelighting device 2, a rotational speed measurement signal 5 of arotational speed measuring device 4 and a temperature measurement signalof a temperature sensor 9. The temperature sensor 9 is arranged inparallel electrically with the lighting device 2 and with the measuringcoil 8 of the rotational speed measuring device 4. Moreover, the controlor regulating circuit of FIG. 5 corresponds in design and function tothe control or regulating circuit of FIG. 3, wherein the constantcurrent source or constant voltage source 11 is designed to receive amixed electric signal, which also comprises, in addition to therotational speed measurement signal 5 of the rotational speed measuringdevice 4, the variable electric temperature measurement signal generatedby the temperature sensor 9, and to correct this variable electrictemperature measurement signal by means of a second variable electriccorrection signal, such that the substantially constant electric signal5′ is provided for the power supply to the lighting device 2. Further,the evaluation unit 12 is designed to determine the temperature measuredby the temperature sensor 9 on the basis of the second variable electriccorrection signal of the constant current source or a constant voltagesource 11 in addition to determining the rotational speed of the driveelement 3.

The invention is not limited to the embodiments described here butinstead includes all embodiments that apply or include the basicanalogous function principle of the invention. In addition, all thefeatures of all the embodiments described and illustrated here can becombined with one another.

What is claimed is:
 1. A medical or dental handpiece, comprising: a rotatable drive element to drive a tool that can be connected to the handpiece, a rotational speed measurement device which is designed to generate a variable electric rotational speed measurement signal assigned to a rotational speed of the drive element, a lighting device that can be supplied with electric power for emitting radiation onto a treatment site, and at least one shared electric line, which is configured (1) to transmit electric power to the lighting device and (2) to transmit the rotational speed measurement signal of the rotational speed measurement device.
 2. The medical or dental handpiece according to claim 1, wherein the rotational speed measurement device comprises one of: a capacitive rotational speed measurement device, an optical rotational speed measurement device, and an inductive rotational speed measurement device.
 3. The medical or dental handpiece according to claim 1, wherein the lighting device and the rotational speed measurement device are arranged electrically in series.
 4. The medical or dental handpiece according to claim 1, comprising a temperature sensor which is arranged electrically in parallel with the lighting device and is designed to generate a variable electric temperature measurement signal, wherein the shared electric line is further configured to transmit the temperature measurement signal.
 5. The medical or dental handpiece according to claim 1, wherein the drive element comprises a rotor that can be driven by a compressed gas.
 6. The medical or dental treatment device according to claim 1, wherein the at least one shared electric line connects the lighting device and at least a part of the rotational speed measuring device to an electric power source.
 7. A medical or dental treatment device, comprising: a medical or dental handpiece according to claim 1, and an electric power source configured to supply a substantially constant electric signal to the lighting device.
 8. The medical or dental treatment device according to claim 7, comprising an evaluation unit for determining the rotational speed of the drive element on the basis of at least one of: the variable electric rotational speed measurement signal generated by the rotational speed measurement device; and a variable electric correction signal generated by the electric power source.
 9. The medical or dental treatment device according to claim 8, comprising a control- and/or regulating unit which is designed to control and/or to regulate the rotational speed of the drive element based on the rotational speed determined by the evaluation unit.
 10. The medical or dental treatment device according to claim 7, wherein the electric power source comprises an electric or electronic regulating device.
 11. A micro-controller operated method for determining the rotational speed of the drive element of a medical or dental handpiece, wherein the medical or dental handpiece comprises a rotational speed measurement device to generate a variable electric rotational speed measurement signal assigned to the rotational speed of the drive element and at least one shared electric line in the medical or dental handpiece, the method comprising: transmitting electric power for the lighting device for emitting radiation onto a treatment site over the at least one shared electric line; and transmitting a rotational speed measurement signal of the rotational speed measurement device towards an evaluation unit over the at least one shared electric line.
 12. An electric control or regulating circuit for controlling or regulating the rotational speed of a drive element of a medical or dental handpiece, wherein the electric control or regulating circuit has a shared electric line for shared transmission of electric power of a first electric power source and an electric signal of a second, different electric power source, wherein the first electric power source comprises an electric power source for supplying power to a lighting device of the medical or dental handpiece and the second electric power source comprises a rotational speed measuring device of the medical or dental handpiece so that over the shared electric line (1) electric power can be transmitted to the lighting device of the medical or dental handpiece and (2) an electrical rotational speed measurement signal can be transmitted from the rotational speed measuring device of the medical or dental handpiece.
 13. The electric control or regulating circuit according to claim 12, wherein at least a portion of the shared electric line is arranged in the medical or dental handpiece.
 14. The electric control or regulating circuit according to claim 12, wherein the electric power source for supplying power to a lighting device comprises a constant current source and/or a constant voltage source which is designed to supply the lighting device with a substantially constant electric signal.
 15. The electric control or regulating circuit according to claim 12, wherein the shared electric line connects the electric power source for supplying power to the lighting device with the lighting device and wherein the shared electric line connects the rotational speed measuring device with the electric power source for supplying power to the lighting device to transmit the electrical rotational speed measurement signal of the rotational speed measuring device to the electric power source for supplying substantially constant power to the lighting device.
 16. The electric control or regulating circuit according to claim 14, wherein the constant current source and/or a constant voltage source comprises an electric or electronic regulating device.
 17. The electric control or regulating circuit according to claim 12, further comprising an evaluation unit for determining the rotational speed of the drive element on the basis of at least one of: the rotational speed measurement signal generated by the rotational speed measurement device; a variable electric correction signal generated by the electric power source for supplying power to a lighting device.
 18. The electric control or regulating circuit according to claim 12, wherein the lighting device and the rotational speed measurement device are arranged electrically in series.
 19. The electric control or regulating circuit according to claim 12, wherein the electric power which is transmitted to the lighting device of the medical or dental handpiece and the electrical rotational speed measurement signal are transmitted over the shared electric line superimposed and/or simultaneously. 